Creepage device



March 13, 1962 J. 5. SCHEURICH CREEPAGE DEVICE 5 Sheets-Sheet 1 Original Filed Oct. 22, 1959 John S Sgheun'ch C?v (5 Maw/Q W 4 March 13, 1962 J. s. SCHEURICH 3,024,769

CREEPAGE DEVICE Original Filed Oct. 22, 1959 3 Sheets-Sheet 2 SILBIS March 13, 1962 J. 5. SCHEURICH CREEPAGE DEVICE 3 Sheets-Sheet 3 nmm OmnN y wmmm mmom

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Original Filed Oct. 22

United rates Patent @flice 3,624,769 Patented Mar. 13, 1962 claims. c1. 121-38) This invention relates generall yto power drives, and, more particularly, it pertains to proportional control devices for a motor drive.

This application is a division of US. Patent Application, Serial Number 848,163 filed on October 22, 1959, by Myron J. Bauer et al. for Guided Missile Launching System.

In any power driven device of large size which requires smooth accurate stoppage of motion, the factor of inertia is to be reckoned with. This is generally true in automatic machines where the skill of an operator in creeping up on a stop position is lacking.

It is, therefore, an object of this invention to provide a motion terminating control for a motor drive.

Another object of this invention is to provide an automatic decelerating stop for a chain conveyor.

Still another object of this invention is to provide a rate controlled stop for an extendable piston rod.

These and other objects and attendant advantages of this invention will become more readily apparent and understood from the following detailed specification and accompanying drawings in which:

FIG. 1 is a schematic of a loader drive, cam and op: erating valves therefor:

FIG. 2 is a cross section of a detail of a control cam and difierential;

FIG. 3 is a schematic diagram of the basic elements which control the movement of a loader drive; and

FIG. 4 is a sectional view, partly in elevation, of a creepage piston.

Creepage control is an arrangement provided in a conveyer system, such as is used in a guided missile launching system, to decelerate its power drive and control the drive chain in its last short distance of travel. This conveyer system has been fully described in copending patent application entitled Loader Mechanism for Guided Missile Launching System, Serial Number 41,219 filed July 6, 1960, by Myron J. Bauer et al., and in the patent application referred to previously for Guided Missile Launching System.

In general, the drive or loader chain is moved along a tramway or loader by a motor driven sprocket. The motor is connected to the sprocket by a hydraulic transmission known as a CAB combination of an A-end and a B-end axial piston pump and motor. As is well-known in hydraulic art, the transmission is controlled by the movement of a tilt plate therein which can be hydraulically positioned by stroking pistons. Mechanical feedback from the driven shaft back to the servo valve through a system of levers, gears, a cam and a differential enables a positioning signal to be introduced. The error or difference between the positioning signal and a neutral condition is then automatically reduced to zero by the arrangement during which time the motive force is applied to the drive chain.

Referring now to FIG. 1 of the drawings, there is shown therein a hydraulic transmission 2258. This transmission 2258 has an input and output consisting of an A-end shaft 2262 and a B-end shaft 2264. A continuously running motor and a chain drive sprocket, neither of which are shown, connect to these shafts 2262 and 2264, respectively.

A servo valve 2278 in a valve block 2230 controls the flow of hydraulic pressure fluid which flow is limited by a metering valve 2285. A pivoted differential lever 2277 is connected to the servo valve 2278 through a differential lever link 2338. The upper end of differential lever 2277 is provided with a cam follower 2291, which follows a helical groove 2289 on a control barrel cam 2299.

The control barrel cam 2290 contains and is secured to a spider 2351 of a differential 2236, as shown in FIG. 2. A pair of spider gears 2353 on the spider 2351 mesh with an input element or gear 2352 and with a response element or gear 2350. The input element or gear 2352 is symbolically shown provided with a crank.

The response element or gear 2350 is attached to a gear train or B-end response gearing assembly 2282, shown in FIG. 1. This response gearing assembly 2282 is driven by the hydraulic transmission output or B-end shaft 2264 to provide a reversed feedback which is thus introduced into the diiferential 2286 along with an input signal from the symbolic crank.

An input signal, introduced through the symbolic crank, rotates the spider 2351 and the barrel earn 2290. The cam follower 2291 follows the helical groove 2289 and swings the differential lever 2277. The diflerential lever 2277, in turn, shifts the servo valve 2278 from a neutral position by means of the diflerential link 2338.

Hydraulic pressure fluid is ported and conducted to one or the other of two stroking pistons 2396 or 2397, shown in PEG. 1, to cause an A-end tilt plate 2274 of A-end 2263 to be canted. The hydraulic transmission thus is activated and the motor-driven A-end shaft 2262 thereof drives the B-end shaft 2264, providing motive power for the chain drive system of the tramway or loader (not shown) as long as the symbolic crank is rotated.

When the cranking ceases, the feedback progresses only until the differential 2286 brings the differential lever 2277 and servo valve 2278 to a neutral position. Thereupon, the tilt plate 2274 is centered and the power output from B-end shaft 2264 stops.

A shaft 2276 and an arm or response cam 2275 project from the titl plate 2274. The lower or pivot end of the differential lever 2277 is pivoted on this cam 2275. The lever 2277 thus has a moving pivot or A-end response. Any displacement of the upper or differential end of the lever 2277 is thus followed by an equal and opposite displacement of the lower or tilting box end in a continuing action. Motion of the linkage subsides only after the servo valve 2278 returns to its neutral position.

The symbolic crank, which was mentioned in the previous discussions of FIGS. 1 and 2, as connected to the input element or gear 2352, is replaced in FIG. 3 With a differential shaft 2321. Differential shaft 2321 is provided with a spur gear 2319 which meshes with a long pilot rack 2310. A pilot rack piston 2323 is attached to one end of the pilot rack 2310 within a pilot rack cylincler 2325.

A spring-centered solenoid controlled loader selector valve 2382 operates the pilot rack piston 2323. If the selector valve 2382 is electrically actuated, pressure fluid is ported to each side of the differential area pilot rack piston 2323 which extends. Now spur gear 2319 introduces an error signal to the differential 2286 which is analogous to that produced by the previously mentioned symbolic crank.

Fluid fiow is purposely restricted to control the rate at which the rack 2310 extends. This rate of signal input is somewhat higher than the previously mentioned metering valve 2335 will allow the transmission 2258 to follow and assures that the latter will assume rate acceleration control.

The travel of the pilot rack 2310 driven through the differential 2286 from the Bend response gearing assembly 2232 represents an equivalent travel of the conveyer drive chain. The end of the pilot rack 23 remote from its piston 2323 is made to travel within a right pilot rack cylinder 2327 equal in length to the left pilot rack cylinder 2325.

If an obstruction, such as a pilot rack stop 2317, is introduced within this right rack cylinder 2327, it too will bring the pilot rack 2310 to a halt and the conveyer drive chain will also halt at a proportional distance of travel. The ends of the right cylinder 2327 accordingly are the limit of travel of the rack 2310 and of the conveyer drive chain movement range too.

Inasmuch as the driven loader drive chain 2004, in the present example, runs at a speed of twelve feet per second, with a deceleration rate of nine feet per second per second, the loader chain will be traveling at a speed of three feet per second when it is only six inches from the end of travel. This velocity is undesirable, and it is necessary to limit the velocity of travel of the chain 2004 to twelve inches per second for the last eight inches of chain travel.

A creepage control valve 2092 is located adjacent to the loader chain 2004, which is of link and roller construction. As shown by dashed lines in FIG. 3, the loader chain 2004 may be cut away at selected places along its length. The creepage control valve 92 is provided with a cam roller 2114 and an actuator arm 2116 which allow it to be mechanically operated by the contour of the loader chain 2004. The dropping or raising of the spring-loaded cam roller 2114 into or out of a cutaway portion of the loader chain 20% causes the creepage control valve 2ti92 to port hydraulic pressure fluid to one side or the other of a creepage piston 20%.

The creepage control piston 2093 is mounted on the end of the right pilot rack cylinder 2327, as shown in FIGS. 3 and 4. The creepage piston 2093 stops the pilot rack 2310 near the end of the load travel and then permits it to travel the last short distance at a governed rate of speed.

This creepage control piston 2993, shown in detail in FIG. 4, is housed in a piston block 2436 which is secured to the end of the right pilot rack cylinder 2327. A cover 2437 is bolted to the other end of this piston block 2436, which also mounts a signal switch SILBlS, a switch actutor lever 2438, and an orifice plug 243%.

In standby condition, the right end of the creepage control piston 20%, as viewed in FIG. 3, is connected to servo pressure fluid and the left end thereof to tank through the creepage control valve 2092. After the pilot rack 23 10 contacts the creepage piston 2093, the transmission 2258 decelerates the chain drive until the cam roller 2114 of the creepage control valve 2092 enters the cam surface cutout of the loader chain 2004-.

At this position, the creepage control valve 2092 releases the pressure fluid on the right side of the creepage piston 2096 through the fixed orifice of the orifice plug 2439 to tank. Servo pressure fluid is then ported to the other side of the creepage piston 2693. The pilot rack 2310 and the loader chain 2664 continue to move forward the remaining short distance of travel with the fluid discharging orifice of the orifice plug 2439 controlling the velocity thereof.

While this invention has been described in connection with a conveyer, its use is by no means limited to such devices. For example, the teachings herewith are equally adaptable to any situation wherein a mechanical motion device is to be decelerated, such as a tool on the ways of a lathe-type machine. Nor is the application of these principles limited to linear motion devices. The driven element may conceivably be a rotary turrent on a swin ing door which is to be brought to a gradual stop.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A motion terminating control for decelerating and stopping the movement of an object, comprising, a system for producing a signal representative of the desired position of said object and for causing said object to move to said desired position, removable restraining means for controlling the terminal velocity of said signal producing system, means controlled by the actual position of said object for removing said restraining means whereby the removal of said restraining means will be dependent on the actual position of said object.

2. A motion terminating control for decelerating and stopping the movement of an object, comprising, a mechanical system for producing a signal representative of a desired position of said object and for causing said object to move to said desired position, restraining means having a first and a second position, interposed in the path of said mechanical signal producing system, means controlled by the actual position of said object for causing said restraining means to move from said first position to said second position allowing said signal producing system to follow the movement of said restraining means whereby the movement of said restraining means will be dependent on the actual position of said object.

3. A motion terminating control for decelerating and stopping the movement of an object, comprising, a system including a movable pilot rack for producing a signal representative of the desired position of said object and for causing said object to move to said desired position, restraining means removable at a predetermined rate interposed in the path of said pilot rack, means responsive to the actual position of said object for causing the removal of said restraining means whereby said restraining means will prevent the movement of said rack past a fixed point until said object reaches a predetermined position and then said restraining means will be removed at a predetermined rate allowing said rack to continue its movement at said predetermined rate.

4. A motion terminating control for decelerating and stopping the movement of an object, comprising, a system including a movable pilot rack for producing a signal representative of the desired position of said object and for causing said object to move to said desired position, hydraulically operated restraining means removable at a predetermined rate interposed in the path of said pilot rack, a hydraulic valve responsive to the actual position of said object for controlling the operation of said restraining means whereby said restraining means will prevent the movement of said rack past a fixed point until said object reaches a predetermined position whereupon said restraining means will be removed at a predetermined rate allowing said rack to continue its movement at said predetermined rate.

5. A motion terminating control for decelerating and stopping the movement of an object, comprising a system including a hydraulically powered movable pilot rack for producing a signal representative of the desired position of said object and for causing said object to move to said desired position, hydraulically operated piston means having a first position and a second position, said first position being intermediate the length of intended travel of said pilot rack rod and said second position being at the extreme limit of intended travel of said pilot rack rod, said piston meansincluding an orifice to limit the rate of movement from said first position to said second position to a predetermined rate, a source of hydraulic pressure connected to said piston and a valve for controlling the application of said pressure to either one or the other of the sides of said piston, said valve including actuating means operably connected to said object and responsive to the position of said object whereby said piston will be maintained in the first of said positions and will obstruct the path of said pilot rack until 6 such time as said object reaches a predetermined position 1,993,475 Butterfield Mar. 5, 1935 at which time said piston will be allowed to move at a 2,028,089 Erling Jan. 14, 1936 fixed rate to said second position and such movement 2,132,721 c1 k O t. 11, 1938 will eontrol the rate of travel of said object to its final 2,361,460 Daugherty 0 31 1944 P 5 2,561,023 Kane July 17, 1951 2,601,760 Swartz et a1. July 1, 1952. References Cited in the file of this patent 2,631,480 Romine et a1. Man 17 1953 UNITED STATES PATENTS 2,700,873 Carlson Feb. 1, 1955 99 7 5 Osmer Sept 29 1 0 10 208521965 Wallace p 1958 

